TUESDAY, March 1 (Health.com) — Charlie Sheen's recent and very public unraveling has all the makings of a bad—yet riveting—TV movie. After months of tabloid drama that included a trashed hotel suite, a divorce filing, and a hospitalization following a reported two-day drug binge, Sheen's hit show, Two and a Half Men, was cancelled for the remainder of the season by CBS executives last week after the star lashed out at its creator in a pair of on-air rants.

In a series of bizarre interviews this week, Sheen appeared increasingly unhinged as he discussed his drug use and his feud with CBS. On the Today Show, he described himself as a "total freaking rock star from Mars" and implied that he had "tiger blood" and "Adonis DNA." On ABC, he said that he was as a "Vatican assassin warlock" and admitted to using a drug, "a drug called Charlie Sheen."

This apparent combination of erratic behavior, delusions, and grandiosity—"I'm grandiose," he told TMZ—has prompted speculation that Sheen may be suffering from bipolar disorder or psychosis brought on by drug use.

Sheen, who has been in rehab in the past, says he is no longer using drugs and passed at least two drug tests given to him by media organizations on Monday. And he has dismissed rumors that he has bipolar disorder, a mental disorder characterized by alternating bouts of depression and a revved-up, better-than-good feeling known as mania.

However, several psychiatrists—who have not treated Sheen and have no direct knowledge of his case—say the actor's public behavior could be consistent with the symptoms of one or both conditions.

"When someone seems like they're operating at the wrong speed, [and] they appear to be grandiose and somewhat irritable and irrational, there are a number of things that would need to be considered," says Kenneth Robbins, MD, a clinical professor of psychiatry at the University of Wisconsin School of Medicine and Public Health in Madison.

Bipolar disorder, sometimes also known as manic depression, is the condition that has been mentioned most often in connection with Sheen. Although all forms of bipolar disorder have some elements of depression and mania, these moods can appear with varying degrees of severity.

In milder cases, the symptoms of mania—lots of energy, euphoria, and little need for sleep—can fall within the range of normal behavior. "These are the stockbrokers who are able to go, go, go, and take some risks," says Aly Hassan, MD, an assistant professor of psychiatry at the University of Nebraska Medical Center in Omaha. "They have no break from reality."

In severe cases, however, people in the grip of a manic episode may seem delusional and exhibit symptoms of psychosis "outside of what we call reality," says psychiatrist Ihsan Salloum, MD, the chief of the division of alcohol and substance abuse at the University of Miami School of Medicine. "In its extreme stages...they think they are Superman or God, and sometimes they could become psychotic to the point where they start hearing voices and becoming paranoid."

Bipolar disorder generally first appears in a person's 20s or 30s or even late teens, experts say. (Sheen is 45.) But especially when it's not severe, the condition is often misdiagnosed and can go unrecognized for decades, Dr. Salloum says.

Sheen has denied having bipolar disorder. When an ABC News reporter brought up the rumors, the actor replied that he is "bi-winning" and suggested that his brain is "maybe not from this particular terrestrial realm."

Even though this denial might seem like still more evidence of bipolar disorder, other conditions besides bipolar could help explain Sheen's behavior. Another possibility, in light of his admitted history of drug use, is psychosis induced by stimulants such as cocaine and amphetamines, which can produce symptoms eerily reminiscent of a bipolar manic episode.

Powerful stimulants "induce hypervigilance, irritability, impulsivity, [and] sometimes megalomania—grandiose behavior," Dr. Hassan says. "People feel in control of things, and this may be when they get into physical combativeness."

Hallucinations, delusions, and other symptoms of psychosis occur in a high proportion of chronic cocaine users, research suggests, and people who use crack cocaine appear to be even more vulnerable. Sheen has admitted using crack and, in an apparent reference to the drug, told ABC that he had been "banging 7-gram rocks."

It can be difficult to untangle the symptoms of bipolar disorder from the effects of substance use, however, because the majority of bipolar people—as high as 80%—also have substance-abuse problems, Dr. Hassan says.

Many people with bipolar disorder enjoy the feeling of being "out of control and on top of the world" that manic episodes can bring, Dr. Hassan says, and they sometimes resort to stimulants such as cocaine and methamphetamine as "a way of perpetuating that state of mania all the time."

Bipolar disorder and illegal drugs aren't the only possible explanations for the type of behavior Sheen has been displaying. Symptoms of withdrawal from alcohol or a sedating drug such as Xanax can sometimes mimic mania, Dr. Robbins says, as can the side effects of steroid drugs, which are often taken for legitimate medical reasons.

Medical conditions unrelated to drugs (prescription or otherwise) can also create a mania-like effect, Dr. Robbins adds. For instance, an overactive thyroid gland (hyperthyroidisim) can cause nervousness and restlessness, although these symptoms are accompanied by other telltale signs and are generally less pronounced than the erratic behavior Sheen has exhibited.

Of all of the possibilities, bipolar disorder and substance abuse are perhaps the most difficult to treat, Dr. Robbins says.

Mood stabilizers and other medications for bipolar can be quite effective, but getting bipolar patients to stick to their treatment regimen can be a challenge, Dr. Robbins says. When patients begin to experience the early, mild stages of mania (known as hypomania), for instance, they sometimes start to feel so good that they stop taking their medication because they think they don't need it anymore.

Similarly, if a person exhibiting the symptoms of mania is not yet being treated for bipolar disorder, it can be difficult to persuade him or her that it's necessary. "Part of the reason people don't seek treatment is they lack the insight to recognize they have an illness," Dr. Robbins says. "When you have a delusion—a fixed false belief—you believe it to be true. When someone tells you to get treatment and you have a delusion, you are likely to believe they just don't get it."